Process for preparing Si-H-containing silanes

ABSTRACT

Silanes of the general formula (1)
 
R a SiH b X 4-b-a   (1)
 
are prepared by disproportionating at least one more highly chlorinated silane in the presence of a homogeneous catalyst in an apparatus with at least one reactive distillation column and at least one additional reactor selected from among prereactors and side reactors, where
     R is an alkyl, aryl, alkaryl or haloalkyl radical,   X is a halogen atom,   a is 0 or 1, and   b is 2, 3 or 4.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a process for preparing hydrogen-containingsilanes by disproportionation of a more highly chlorinated silane in thepresence of a homogeneous catalyst.

2. Background Art

The demand for the organylhydrogenchlorosilanes MeSiHCl₂ and Me₂SiHCl issignificantly higher than the amount in which they are obtained asby-products in the direct synthesis by the Müller-Rochow process.

EP 286074 A describes a process for the disproportionation of MeSiHCl₂to give MeSiH₃ in the presence of a heterogeneous catalyst in adistillation column. In the process, the heterogeneous catalyst has alimited operating life. To replace the catalyst, it is at leastnecessary to take the portion of the plant charged with the catalyst outof operation in order for the catalyst to be regenerated in thedistillation column. Opening of the distillation column and replacementof the catalyst by fresh catalyst is also frequently necessary.

EP 685483 A describes the disproportionation of MeSiHCl₂ to give MeSiH₃in the presence of a homogeneous catalyst in a distillation column.However, the poor space-time yield and the high energy consumption standin the way of the commercialization of the process.

DE 102004045245 A1 describes the disproportionation of HSiCl₃ to prepareSiH₄ in the presence of a heterogeneous catalyst in a distillationcolumn provided with at least one side reactor. The heterogeneouscatalyst is located in the side reactor and can therefore be replacedmore simply.

SUMMARY OF THE INVENTION

It has now been surprisingly discovered that hydrogen-containing silanesmay be obtained from more highly chlorinated silanes bydisproportionation employing a homogenous catalyst, a reactivedistillation column, and at least one prereactor or side reactor. Lowenergy consumption and high space time yields are achievable by theprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of a subject invention process inschematic form;

FIG. 2 illustrates a further embodiment of one aspect of the subjectinvention process;

FIG. 3 illustrates one embodiment of the subject invention processemploying a side reactor; and

FIG. 4 illustrates a prior art process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The invention provides a process for preparing silanes of the generalformula (1)R_(a)SiH_(b)X_(4-b-a)  (1)by disproportionation of at least one more highly chlorinated silane inthe presence of a homogeneous catalyst in an apparatus which is equippedwith at least one reactive distillation column and at least oneadditional reactor selected from among prereactors and side reactors,where

-   R is an alkyl, aryl, alkaryl or haloalkyl radical,-   X is a halogen atom,-   a is 0 or 1 and-   b is 2, 3 or 4.

In the present homogeneous process, the combination of prereactor orside reactor with the reactive distillation column and the resultingincreased residence time reduces the energy consumption by up to 30%compared to purely a reactive distillation column. Apart from theimproved energy consumption, the conversion can be increased at anidentical energy input by the combination of reactive distillationcolumn and side reactor/prereactor.

The space-time yields reach values which have been able to be achievedonly with heterogeneous catalysts. Here, the homogeneous catalysts bringthe advantage that they are pumpable in neat or dissolved form. Thismakes the process for carrying out the reaction simpler since thecatalyst can also be introduced during ongoing operation of the process,i.e. the catalyst concentration can be increased or reduced, thecatalyst can be renewed or replaced by another homogeneous catalyst asrequired.

The additional reactor can be configured as a prereactor or sidereactor. Here, the term “prereactor” refers to a reactor in which atleast one feed stream is fed into the prereactor and at least onesubstream is taken from the prereactor and introduced into the reactivedistillation column. Direct recirculation of substreams from thereactive distillation column into the prereactor does not take place.The term “side reactor” refers to a reactor in which at least one streamis taken from the reactive distillation column and fed into the sidereactor and at least one stream is recirculated from the side reactorinto the reactive distillation column. Direct introduction of feedstreams into the side reactor does not take place.

Examples of R are alkyl radicals such as the methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl,neopentyl, and tert-pentyl radicals; hexyl radicals such as the n-hexylradical; heptyl radicals such as the n-heptyl radical; octyl radicalssuch as the n-octyl radical and isooctyl radicals such as the2,2,4-trimethylpentyl radical; nonyl radicals such as the n-nonylradical; decyl radicals such as the n-decyl radical; dodecyl radicalssuch as the n-dodecyl radical; tetradecyl radical; hexadecyl radicalsand octadecyl radicals such as the n octadecyl radical; cycloalkylradicals such as cyclopentyl, cyclohexyl, cycloheptyl andmethylcyclohexyl radicals; aryl radicals such as the phenyl radical;alkaryl radicals such as the o-, m-, p-tolyl radicals, xylyl radicals,and ethylphenyl radicals; and aralkyl radicals such as the benzylradical, the α- and ω-phenylethyl radicals; haloalkyl radicals such asthe chloromethyl, 3-chloropropyl and 3-bromopropyl radicals; andhaloaryl radicals such as the o-, m-, and p-chlorophenyl and chlorotolylradicals.

The radical R preferably has from 1 to 18 carbon atoms, more preferablyfrom 1 to 6 carbon atoms. In particular, the radical R is a methyl orphenyl radical.

The halogen atom X is preferably chlorine, bromine or iodine.

Preference is given to carrying out the disproportionation reactions(1), (2) and (3) starting from SiHCl₃:2SiHCl₃→SiH₂Cl₂+SiCl₄  (1),3SiHCl₃→SiH₃Cl+2SiCl₄  (2),4SiHCl₃→SiH₄+3SiCl₄  (3).

Particular preference is given to carrying out the disproportionationreactions (4) and (5) starting from MeSiHCl₂:2MeSiHCl₂→MeSiH₂Cl+MeSiCl₃  (4),3MeSiHCl₂→MeSiH₃+2MeSiCl₃  (5).

The silanes of the general formula (1) as set forth in claim 1 arepreferably used for preparing silanes selected from among MeSiHCl₂ andMe₂SiHCl.

The homogeneous catalyst preferably contains at least one fullyorganically substituted ammonium, phosphonium or imidazolium unit.Examples are quaternary ammonium and phosphonium salts and positivelycharged heterocycles which have one or more fully organicallysubstituted atoms selected from among nitrogen and phosphorus atoms.Preferred positively charged heterocycles are imidazolium salts andpyridinium salts.

As catalysts, preference is given to using:

-   (a) quaternary ammonium salts of the general formula R¹ ₄NX¹ and-   (b) quaternary phosphonium salts of the general formula R² ₄PX²,    where-   R¹ and R² are each an unsubstituted or halogen-substituted    hydrocarbon radical which may contain heteroatoms and-   X¹ and X² are each a halogen atom.

R¹ and R² can be, for example, branched, unbranched or cyclic alkylradicals and multiple bond systems such as aryl, alkaryl or aralkylradicals. Examples of R¹ and R² are the examples of unsubstituted orhalogen-substituted alkyl, aryl or alkaryl radicals given above for Rand also aralkyl radicals such as o-, m- and p-phenylalkyl radicals. Theradicals R¹ and R² preferably have from 1 to 18 carbon atoms, morepreferably from 1 to 10 carbon atoms, and the radicals R¹ and R² areeach most preferably an alkyl radical having from 2 to 8 carbon atoms.

The halogen atoms X¹ and X² are preferably chlorine, bromine or iodine,in particular chlorine.

The quaternary phosphonium salt is preferably (n-butyl)₃(n-octyl)PCl.The preparation of such homogeneous catalysts by alkylation of tertiaryphosphines by means of alkyl halides is described, for example, inHOUBEN-WEYL, Georg Thieme Verlag, Volume XII/1, pp. 79-90, 1963.

Further preferred catalysts are:

-   (c) imidazolium salts of the general formula

-   (d) pyridinium salts of the general formula

-    where-   R⁸ is hydrogen and has one of the meanings of R¹ and R²,-   R⁷, R⁹ and R¹⁰ each have one of the meanings of R¹ and R² and-   X⁵ and X⁶ each have one of the meanings of X¹ and X².

Further preferred catalysts are:

-   (e) ionic liquids, namely low-melting salts of quaternary ammonium,    quaternary phosphonium, pyridinium and imidazolium cations. Their    preferred melting points at 1 bar are, for the present process, not    more than 150° C., preferably not more than 100° C., particularly    preferably not more than 50° C.

The radicals of the cations of the ionic liquids preferably correspondto the above-described radicals R¹ and R².

The ionic liquids are preferably used as metal or transition metalhalides. The metal and transition metal halides are prepared using, forexample, MX_(e) where M=Ga, Fe, Cu, Zn, In, Ti, Cd, Hg, B, Sn, Pb, Biand X=halogen. However, it is also possible to use other compositions.They contain, for example, the following anions: AlCl₄ ⁻, Al₂Cl₇ ⁻,Al₃Cl₁₀ ⁻, AlEtCl₃ ⁻, Al₂Et₂Cl₅ ⁻, BCl₄ ⁻, BF₄ ⁻, Bet₃Hex⁻, CuCl₂ ⁻,Cu₂Cl₃ ⁻, Cu₃Cl₄ ⁻, SnCl₃ ⁻, Sn₂Cl₅ ⁻, PF₆ ⁻, H₂PO₄ ⁻, SbF₆ ⁻, NO₃ ⁻,HSO₄ ⁻, CH₃SO₄ ⁻, CF₃SO₃ ⁻, (CF₃SO₂)₂N⁻.

Specific examples of ionic liquids are:

-   1-ethyl-3-methylimidazolium chloride-aluminum chloride    (EMIMCL/AlCl₃)-   1-butyl-3-methylimidazolium chloride-aluminum chloride    (BMIMCL/AlCl₃)-   3-methyl-N-butylpyridinium chloride-aluminum chloride    (3-MBPYCL/AlCl₃)-   1-butylpyridinium chloride-aluminum chloride (BPYCL/AlCl₃)    tetra-n-butylphosphonium chloride-aluminum chloride (TBPCL/AlCl₃).

Particular preference is given to imidazolium salts. Suitable ionicliquids and their preparation are described, for example, in DE 10157198A.

It is possible to use pure ionic liquids (e) or a mixture of ionicliquids, or mixtures of ionic liquids (e) with salts selected from amongthe salts (a), (b), (c) and (d). The ionic liquids (e) can alsosimultaneously function as a solvent or solubilizer for salts selectedfrom among the salts (a), (b), (c) and (d). The ionic liquids arepreferably used in a proportion of from 0.1 to 80% by weight, inparticular 1-10% by weight, in the reaction mixture with silanes.

The homogeneous catalysts (a), (b), (c) and (d) are soluble in thereaction medium. These catalysts are preferably used neat, as a solutionin a preferably high-boiling inert organic solvent, preferably ahydrocarbon such as tetralin or decalin, or as a solution inhigh-boiling product silanes of the general formula R_(a)SiX_(4-a),where R and X are as defined above.

In the process of the invention, the phosphonium and imidazoliumcatalysts display excellent thermal stability in the variousorganylchlorosilane media and a high catalytic activity in thedisproportionation reactions according to the invention.

The process of the invention can be carried out batchwise,semicontinuously or fully continuously. It is preferably carried outfully continuously. In the process of the invention, thedisproportionation reaction is carried out in an arrangement of reactivedistillation and additional reactor. The arrangement according to theinvention of the two reactors makes it possible to carry out thedisproportionation reaction simply and robustly far beyond the chemicalequilibrium. The additional reactor is used to ensure a sufficientresidence time. The reactive distillation for its part makes it possibleto increase the conversion beyond the chemical equilibrium.

The disproportionation reaction preferably takes place at a pressure offrom 0.1 to 20 bar, in particular 1-5 bar, and preferably at atemperature of preferably from 0 to 250° C., in particular from 25 to150° C.

The silane starting materials are used in gaseous or liquid form or as asolution in an inert organic solvent such as hexane, toluene, xylene orchlorobenzene.

The dichlorosilane and/or monochlorosilane and/or silane prepared in theprocess of the invention by disproportionation of trichlorosilane ispreferably reacted with MeSiCl₃ in a subsequent reaction. The targetproduct MeSiHCl₂ is obtained in high yields in a comproportionationreaction.

The net equation is then:MeSiCl₃+SiHCl₃→MeSiHCl₂+SiCl₄  (6).

Furthermore, the MeSiH₂Cl and/or MeSiH₃ prepared in the process of theinvention by disproportionation of methyldichlorosilane is preferablyreacted with Me₂SiCl₂ in a subsequent reaction. The target productMe₂SiHCl is obtained in high yields in a comproportionation reaction.

The net equation is then:Me₂SiCl₂+MeSiHCl₂→Me₂SiHCl+MeSiCl₃  (7).

The SiH-containing organylchlorosilanes are valuable starting compoundsfor the preparation of functional silanes or siloxanes which areobtained via a hydrosilylation reaction with organic compounds havingaliphatic double or triple bonds. A further use of, for example,dimethylchlorosilane is the preparation of organopolysiloxanes whichhave dimethylhydrogensilyl groups and are used in addition-crosslinkingsilicone rubber compositions.

A preferred embodiment of the process of the invention with a prereactorwill be explained with the aid of FIG. 1:

Starting materials from streams (1) and (13) and catalyst from stream(10) are mixed and introduced via stream (2) into the prereactor (R1),whereupon disproportionation commences straight away. The conversion inthe prereactor (R1) can be increased above the chemical equilibrium byfractional distillation of the reaction products. At the top of theprereactor (R1), the less chlorinated silanes accumulate and are fed asstream (3) to the reactive distillation column (K1). There, they arereacted beyond the chemical equilibrium. The more highly chlorinatedsilanes containing catalyst leave the prereactor (R1) as bottoms instream (4). Starting material also enters the reactive distillationcolumn (K1) via stream (12). The reactive distillation column (K1)receives catalyst via stream (9). The less chlorinated silanes are takenoff as stream (14) from the top of the reactive distillation column(K1). The more highly chlorinated silanes containing catalyst leave thereactive distillation column (K1) as bottoms in stream (5) and are fedtogether with stream (4) as stream (6) to the distillation unit (D1) inwhich they are separated into a silane stream (7) and a catalyst stream(8). The catalyst stream (8) is divided into the streams (9) and (10).The silane stream (7) is fed to a distillation column (K2) from whichhighly chlorinated silanes are discharged at the bottom as stream (15)and the overhead stream (11) comprising less chlorinated silanes isdivided into the streams (12) and (13).

Possible reactor types for the prereactor (R1) are typical liquid-phasereactors as are described, for example, in ULLMANN'S ENCYCLOPEDIA OFINDUSTRIAL CHEMISTRY: 7th edition, 2006. The reactor is particularlypreferably configured as a tube reactor, loop reactor or stirred tankreactor or as a reactive distillation.

The reactive distillation column (K1) can, for example, contain orderedpacking, random packing elements or trays. Furthermore, the liquidholdup in the reactive distillation column (K1) can be increased bymeans of suitable internals such as chimney trays or downcomers.

The silanes of the general formula (1) obtained in thedisproportionation according to the invention can preferably then bereacted further in a comproportionation reaction. The overall processrepresents a conversion of chlorosilanes.

The dichlorosilane and/or monochlorosilane and/or silane prepared in theprocess of the invention by disproportionation of trichlorosilane ispreferably reacted with MeSiCl₃ in a subsequent reaction. The targetproduct MeSiHCl₂ is obtained in high yields in a comproportionationreaction.

Such an overall process using a prereactor is explained as a furtherpreferred embodiment of the process of the invention with the aid ofFIG. 2: The less chlorinated silanes taken off as stream (14) from thetop of the reactive distillation column (K1) are introduced into thecomproportionation reactor (R2) together with more highly chlorinatedsilanes in stream (16) and less chlorinated silanes in stream (18). Thesilane products in stream (17) from the comproportionation reactor (R2)are separated in the distillation column (K3) into a stream (18) of lesschlorinated silanes and a product stream (19) of more highly chlorinatedsilanes. The less chlorinated silanes in stream (18) are recirculated tothe comproportionation reactor (R2).

A preferred embodiment of the process of the invention with a sidereactor is explained with the aid of FIG. 3:

Starting materials are fed as streams (20) and (25) into the reactivedistillation column (K1). The catalyst stream (24) is introduced intothe reactive distillation column (K1). Part of the reaction mixture inthe reactive distillation column (K1) is conveyed through the sidereactor (R3). The disproportionation takes place in the reactivedistillation column (K1) and in the side reactor (R3). There, thestarting materials are reacted beyond the chemical equilibrium. The lesschlorinated silanes are taken off as stream (21) from the top of thereactive distillation column (K1). The catalyst-containing more highlychlorinated silanes leave the reactive distillation column (K1) asbottoms in stream (22) and are fed to the distillation unit (D1) inwhich they are separated into a silane stream (23) and a catalyst stream(24). The catalyst stream (24) is recirculated to the reactivedistillation column (K1). The silane stream (23) is fed to thedistillation column (K2) from which highly chlorinated silanes aredischarged at the bottom as stream (26) and the overhead stream (25) ofless chlorinated silanes is recirculated to the reactive distillationcolumn (K1).

An increase in the reaction volume takes place in the side reactor (R3).For this purpose, the liquid phase is collected in the reactivedistillation column (K1) and fed into the side reactor (R3). Theconversion takes place close to the chemical equilibrium in the sidereactor (R3) due to a sufficient residence time. The gas and liquidphases are recirculated from the side reactor (R3) to a suitable pointon the reactive distillation column (K1).

All symbols in the above formulae have their respective meaningsindependently of one another. The silicon atom is tetravalent in allformulae.

In the context of the present invention, all amounts and percentagesare, unless indicated otherwise, by weight, all temperatures are 20° C.and all pressures are 1,013 bar (abs.).

EXAMPLES Example 1 Disproportionation to Prepare Chlorosilanes of theGeneral Formula R_(a)SiH_(b)X_(4-b-a) (1)

a) without Prereactor—not According to the Invention

The disproportionation was carried out in an apparatus as shown in FIG.4. All starting material via stream (1) and all catalyst via stream (8)are fed directly into the reactive distillation column (K1).

b) with Prereactor

The disproportionation was carried out in an apparatus as shown inFIG. 1. When the reaction is carried out in conjunction with theprereactor (R1), the additional reaction volume is provided in theprereactor (R1). The feed mixture of starting material and homogeneouscatalyst is introduced into the prereactor (R1).

Carrying out the reaction with prereactor as per example 1b makes itpossible, when the prereactor is configured as a tube reactor, toachieve a saving in the heating power required of up to 23% and a savingof 25% in the cooling power (see Table 1). Apart from the lower energyconsumption, example 1b) gives a space-time yield which is up to 17%higher than in example 1a), which leads to smaller reactor dimensions.

Table 1:

Relative energy consumption and space-time yield as a function of theinstalled volume of the prereactor at a constant total conversion of theprocess. The first line shows the ratio of the prereactor (R1) to thereaction volume in the reactive distillation (K1). At a ratio of 0, apure reactive distillation as per Example 1a is present for comparativepurposes.

Volume of [—] 0.000 0.048 0.096 0.243 0.488 prereactor/volume ofreactive distillation Relative heating [%] 100.0%  94.5%  91.3%  85.3% 81.4% power Relative cooling [%] 100.0%  94.1%  90.9%  84.6%  80.4%power Relative space- [%] 100.0% 104.6% 107.9% 113.8% 116.5% time yield

TABLE 2 Main constituents of the streams from Example 1 for thedisproportionation of SiHCl₃ and MeSiHCl₂ Stream SiHCl₃disproportionation MeSiHCl₂ disproportionation 1 SiHCl₃ MeSiHCl₂ 2SiHCl₃; catalyst MeSiHCl₂ 3 SiH₃Cl; SiH₂Cl₂; SiHCl₃ MeSiH₂Cl; MeSiHCl₂ 4SiHCl₃; SiCl₄; catalyst MeSiHCl₂; MeSiCl₃; catalyst 5 SiHCl₃; SiCl₄;catalyst MeSiHCl₂; MeSiCl₃; catalyst 6 SiHCl₃; SiCl₄; catalyst MeSiHCl₂;MeSiCl₃; catalyst 7 SiHCl₃; SiCl₄ MeSiHCl₂; MeSiCl₃ 8 Catalyst Catalyst9 Catalyst Catalyst 10 Catalyst Catalyst 11 SiHCl₃ MeSiHCl₂ 12 SiHCl₃MeSiHCl₂ 13 SiHCl₃ MeSiHCl₂ 14 SiH₄; SiH₃Cl; SiH₂Cl₂ MeSiH₃ 15 SiCl₄MeSiCl₃

Example 2 Disproportionation to Prepare Chlorosilanes of the GeneralFormula R_(a)SiH_(b)X_(4-b-a) (1) with Side Reactor

The disproportionation was carried out in an apparatus as shown in FIG.3.

TABLE 3 Main constituents of the streams from Example 2 for thedisproportionation of SiHCl3 and MeSiHCl2 Stream SiHCl₃,disproportionation MeSiHCl₂ disproportionation 20 SiHCl₃ MeSiHCl₂ 21SiH₄; SiH₃Cl; SiH₂Cl₂ MeSiH₃ 22 SiHCl₃; SiCl₄; catalyst MeSiHCl₂;MeSiCl₃; catalyst 23 SiHCl₃; SiCl₄ MeSiHCl₂; MeSiCl₃ 24 CatalystCatalyst 25 SiHCl₃ MeSiHCl₂ 26 SiCl₄ MeSiCl₃

Example 3 Process for the Conversion of Chlorosilanes of the GeneralFormula R_(a)SiH_(b)X_(4-b-a) (1) using a Prereactor

The disproportionation was carried out in an apparatus as shown in FIG.2.

TABLE 4 Main constituents and mass flows of the streams from Example 3MeSiHCl₂ disproportionation SiHCl₃ Mass flow Stream disproportionationConstituents kg/h 1 SiHCl₃ MeSiHCl₂ 10.0 2 SiHCl₃; catalyst MeSiHCl₂11.4 3 SiH₃Cl; SiH₂Cl₂; SiHCl₃ MeSiH₂Cl; MeSiHCl₂ 2.4 4 SiHCl₃; SiCl₄;catalyst MeSiHCl₂; MeSiCl₃; 9.0 catalyst 5 SiHCl₃; SiCl₄; catalystMeSiHCl₂; MeSiCl₃; 17.5 catalyst 6 SiHCl₃; SiCl₄; catalyst MeSiHCl₂;MeSiCl₃; 26.4 catalyst 7 SiHCl₃; SiCl₄ MeSiHCl₂; MeSiCl₃ 23.0 8 CatalystCatalyst 3.4 9 Catalyst Catalyst 2.1 10 Catalyst Catalyst 1.4 11 SiHCl₃MeSiHCl₂ 14.7 12 SiHCl₃ MeSiHCl₂ 14.7 13 SiHCl₃ MeSiHCl₂ 0.0 14 SiH₄;SiH₃Cl; SiH₂Cl₂ MeSiH₃; MeSiH₂Cl 1.7 15 SiCl₄ MeSiCl₃ 8.3 16 MeSiCl₃Me₂SiCl₂ 18.1 17 SiH₄; SiH₃Cl; SiH₂Cl₂; MeSiH₃; MeSiH₂Cl; 30.1 SiHCl₃;MeSiHCl₂; MeSiHCl₂; Me₂SiHCl; MeSiCl₃ Me₂SiCl₂ 18 SiH₄; SiH₃Cl; SiH₂Cl₂MeSiH₃; MeSiH₂Cl 10.4 19 SiHCl₃; MeSiHCl₂; MeSiHCl₂; Me₂SiHCl; 19.7MeSiCl₃ Me₂SiCl₂

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. A process for preparing silanes of the formula (1)R_(a)SiH_(b)X_(4-b-a)  (1) comprising disproportionating at least onemore highly chlorinated silane in the presence of a homogeneous catalystin an apparatus which is equipped with at least one reactivedistillation column and at least one additional prereactor and/or sidereactor, where R is an alkyl, aryl, alkaryl or haloalkyl radical, X is ahalogen atom, a is 0 or 1 and b is 2, 3 or
 4. 2. The process of claim 1,wherein the radical R is a methyl or phenyl radical and the halogen atomX is chlorine.
 3. The process of claim 1, wherein at least one ofdisproportionation reaction (1), (2) and (3) starting from SiHCl₃ arecarried out:2SiHCl₃→SiH₂Cl₂+SiCl₄  (1),3SiHCl₃→SiH₃Cl+2SiCl₄  (2),4SiHCl₃→SiH₄+3SiCl₄  (3).
 4. The process of any of claim 1, wherein atleast one of disproportionation reaction (4) and (5) starting fromMeSiHCl₂ are carried out:2MeSiHCl₂→MeSiH₂Cl+MeSiCl₃  (4),3MeSiHCl₂→MeSiH₃+2MeSiCl₃  (5).
 5. The process of claim 1, wherein thesilanes of the formula (1) are used for preparing silanes MeSiHCl₂ andMe₂SiHCl.
 6. The process of claim 1, wherein the homogeneous catalystcomprises at least one fully organically substituted ammonium,phosphonium or imidazolium moiety.
 7. The process of claim 1, whichemploys a prereactor, there being no direct recycle of a substream fromthe reactive distillation column into the prereactor.
 8. The process ofclaim 1, wherein a prereactor and a side reactor are employed.
 9. Theprocess of claim 1, wherein the homogenous catalyst comprises a catalystdissolved in an ionic liquid.
 10. The process of claim 1, wherein thehomogenous catalyst is an ionic liquid.
 11. The process of claim 10,wherein said ionic liquid comprises a salt of a quaternary ammonium,quaternary phosphonium, pyridinium, or imidazolium cation, or mixturethereof, the ionic liquid having a melting point of not more than 150°C.
 12. The process of claim 1, wherein the catalyst comprises at leastone of: 1-ethyl-3-methylimidazolium chloride-aluminum chloride;1-butyl-3-methylimidazolium chloride-aluminum chloride;3-methyl-N-butylpyridinium chloride-aluminum chloride; 1-butylpyridiniumchloride-aluminum chloride; and tetra-n-butylphosphoniumchloride-aluminum chloride.
 13. The process of claim 1, wherein thecatalyst is supplied as a solution in a high boiling inert organicsolvent.
 14. The process of claim 13, wherein the high boiling inertsolvent comprises at least one of tetralin or decalin.
 15. The processof claim 1, further comprising removing a stream of less chlorinatedsilanes from the top of the reactive distillation column and introducingthe less chlorinated silanes into a comproportionation reactor, feedinga product stream from the comproportionation reactor into a distillationcolumn, and separating the product stream into respective furtherproduct streams of less chlorinated silanes and more chlorinatedsilanes.